The instant invention concerns an open-end spinning machine with a plurality of spinning stations located next to each other, having spinning elements driven collectively by a collective drive, and a process for thread joining on such a machine. In a known process, thread joining is carried out at reduced rotor speed, whereby the speed of fiber feeding and thread drawoff is adapted to this reduced number of RPMs of the rotor in such a way that the rotor speed ratio between the individual spinning elements is maintained at all times as it was preset for spinning production (German Pat. DE-OS No. 2,058,604, corresponding with U.S. Pat. No. 3,791,128). In order to attain this reduced rotor speed for thread joining at an individual spinning station in a simple manner when a plurality of spinning stations are driven collectively, the RPM's of the spinning rotor are scanned during run-up to production speed, and the thread joining process is started when the reduced number of RPMs is reached (German Pat. DE-AS No. 2,341,528, corresponding with U.S. Pat. No. 4,276,741 and DE-OS No. 2,610,575). However, the time available here and also the number of RPMs are not constant and vary in particular depending upon the running condition of the machine and of the individual rotor bearings. This not only influences the success of thread joining but also the speed and the quality of the joints.
Another known method consists in providing a step-up gearing between a drive belt and the rotor shaft for each spinning station and to preset two step-up ratios which can take over the driving of the spinning rotor alternately for thread joining or for production, as desired (German Pat. DE-OS No. 2,754,785, Japanese Pat. JP-PS-AS No. 21.966/84. Although rotor speed is thus reduced by a certain percentage for thread joining, this speed is always in a fixed relation to the production speed of the rotor. Thus the rotor speed for thread joining is different from and dependent from production speed.
The instant invention is based upon the surprising finding that the rotor speed for thread joining should not always be uniformly low, and should not always be reduced at a fixed ratio to the production speed of the rotor. The correct rotor speed for thread joining depends in each case upon the fiber material to be spun.
It is therefore the objective of the instant invention to avoid the disadvantages cited above. In particular, it is the objective of the instant invention to create a simple device by means of which a second rotor speed can be attained individually at a spinning station whereby it is possible to select said rotor speed in a simple manner in accordance to spinning conditions, and independently from the production rotor speed.
It is a further objective of the instant invention to create a thread joining process which improves successful piecing and the quality of the joints.
This objective is attained by the invention by providing, in addition to the collective drive, a stationary auxiliary drive which can be attributed to (i.e. associated with) the spinning element of each spinning station individually, instead of the collective drive. The speed of this second, stationary auxiliary drive which can be individually attributed to the spinning elements can be adapted as needed to any given fiber material, rotor diameter, etc. at a central location. Since this adjustment is carried out once per machine or per section, such an adaptation to a different type of fibers is economical from the standpoint of both time and material. The auxiliary drive is preferably located in the end frame of the machine.
The concept of "spinning element", in the sense of the instant invention, shall include all elements required for the spinning process. This is preferably a spinning rotor, but this concept should also comprise, in addition to a spinning rotor, a pair of friction rollers as well as other elements of a spinning station, for example the feed roller, etc.
According to a preferred embodiment of the object of the invention, the auxiliary drive is equipped with a drive motor that is separate from the collective drive. In this way the speed ratio between the two drives can be controlled very simply.
In an alternate embodiment of the invention however, a single drive motor can be provided also and can be attributed to the collective drive directly and to the auxiliary drive via a step-up gear.
In the sense of the invention the concept "step-up gear" is to be understood to mean a gear to step up speed, as well as to reduce speed.
The step-up ratio of the step-up gear can be set as a function of production speed and of the material to be spun, preferably between 95:100 and 75:100, so that the rotation speed of the spinning elements is merely in about the range of and 5% to 25% lower for thread joining than for production.
In many applications a gradual acceleration of the spinning aggregate from thread joining speed to production speed is not required. According to an aspect of this invention, the step-up gear (if present) is preferably equipped with a stepped speed pulley for such case.
The adjustment of the step-up gear is preferably continuous, and a further advantage is achieved if the speed of the auxiliary drive can be increased to the speed of the collective drive.
Experience has shown that even when the fiber feeding device suddenly releases the fiber tuft, the fibers do not reach the spinning element jerkily but that the fiber quantity reaching the spinning element increases according to a run-up curve until finally the fiber quantity per time unit coming into the spinning element is steadily as preset by the feeding speed of the fiber feeding device. Therefore it is preferable to accelerate the auxiliary drive not randomly but according to this run-up curve of the fiber quantity reaching the spinning element upon release of the fiber feeding device.
It is also useful for many purposes if the direction of rotation of the auxiliary drive can be reversed. This applies especially to the friction rollers and the feed roller.
Preferably the auxiliary drive is controlled through controls located on a service unit travelling alongside a plurality of spinning stations, whereby the entire thread joining process is controlled through said controls. In a preferred embodiment of the invention the controls on the service unit which control the auxiliary drive are also controllably linked to an auxiliary driving device for the mechanism which draws off the thread during the thread joining process. In this way, the thread draw-off speed can be adjusted to the rotational speed of the spinning element and to the thread joining process. At the same time it is absolutely possible to control the thread draw-off speed asynchronously to the rotational speed of the spinning element, for example in order to give the thread temporarily greater twist for the thread joining process.
According to a preferred embodiment of the invention, the collective drive is equipped with a main drive belt to drive a plurality of spinning elements simultaneously and the auxiliary drive is equipped with an auxiliary drive belt to drive a spinning element individually. The main drive belt drives all normally operating spinning elements at the same speed during production. By contrast, spinning elements in which a thread is to be joined anew are separated from this main drive belt during the thread joining phase and are instead driven individually by the auxiliary drive belt which, in turn, is driven at a speed different from that of the main drive belt. Thus any spinning element at which a thread is to be joined is operating at a rotational speed different from that of the spinning elements operating undisturbed at production speed.
For reason of material and space savings, the auxiliary drive belt can be made narrower than the main drive belt. Since the auxiliary drive belt only drives one single spinning element at a time, functional reliability is nevertheless ensured.
The selection of the desired drive, in each case, for a specific spinning element is made preferably by means of an individual switch-over device which alternately attributes (i.e. drivingly couples) one of the two drives to the spinning element. This switch-over device can be borne upon by an elastic element so that the main drive belt can be brought to bear against a drive element connected to and rotating with the spinning element, or can be held against said drive element when the switch-over device is enabled (i.e. released).
Preferably a two-armed switch-over lever is provided for each spinning station. This lever is equipped with a main contact roller on one arm and with an auxiliary contact roller on the other arm for the alternate application of the main drive belt or of the auxiliary drive belt against the spinning element. In this manner a simple embodiment in accordance with the object of this invention is achieved.
In order to avoid additional operating elements per spinning station, the switch-over is preferably linked in a controllable manner to a brake for the spinning element. This controllable linking can be achieved in various ways. In a preferred embodiment of the device according to invention the brake is attributed to (i.e. comprised of) a brake lever supported by the switch-over lever.
Simple control of the spinning element brake and of the switch-over device is achieved according to this invention by equipping the brake lever with at least one carrier, and through the fact that said brake lever, by moving from a neutral spinning position into its first end position constituting the braking position, lifts the main contact roller from the main drive belt and, by moving into its other end position constituting the thread joining position, causes the auxiliary contact roller to be applied against the auxiliary drive belt.
According to a preferred embodiment according to the object of this invention, the brake lever is pivotably supported on bearings by its one end on the main drive roller supporting shaft of the two-armed lever, is at the same time linked to an activating device by its free end, and is equipped with a braking surface between its two ends. It can be moved into its braking position so that the brake lever, after reaching its braking position and continuing its movement, causes pivoting of the switch-over lever as a result of the application of its braking surface against the spinning element.
It is advantageous if the spinning element is located in immediate proximity of the main contact roller, and further if the distance between the free end of the brake lever (used and for activation) and the brake (which can be brought to bear upon the spinning element) is greater than the distance between the brake and the bearing shaft.
In a preferred embodiment of a device according to this invention, the brake lever is equipped with an intermediate lever which, together with the switch-over lever, is pivotably supported on bearings on a common shaft. One end of said intermediate lever is in gearing contact with the activating device and overlaps the two-armed lever of the switch-over device on its side opposite to the spinning element. The other end of said intermediate lever is articulatedly linked to the brake lever which reaches under the two-armed switch-over lever on its side towards the spinning element. In this manner, in spite of minimal switching paths, only little switching force is required.
In order to lower the drive forces for activation of the brake and of the switch-over device by properly selecting lever arms and drive moments, and in order to raise operational security the brake lever is preferably supported on bearings independently from the two-armed lever of the switch-over device, whereby the brake lever is equipped with one carrier on each side of the pivoting axis of the two-armed switch-over lever for the pivoting of the two-armed switch-over lever into one or the other pivoting direction, as desired. Because of the independent bearing support of the brake lever its pivoting point can be selected so as to render the brake's movement essentially linear when it is moved into or out of braking position. This increases operational security of the device.
In a further, preferred development of such an embodiment of the invention, the shaft of a spinning element in the form of a spinning rotor is supported on bearings in a wedge-shaped gap formed by supporting rings, while the brake lever can be moved in its braking movement in the direction of said supporting rings. Under such conditions, space utilization is especially good if the shaft of the spinning rotor is supported by a single pair of supporting rings on the side towards the spinning rotor, in relation to the drive belt and the auxiliary drive belt, and is supported by a combined axial/radial bearing on the side away from the spinning rotor.
In a fully automatic open-end spinning machine, a service unit is normally provided for travelling alongside a plurality of spinning stations, and which can interact as desired with each spinning station. It is advantageous in such instances if the service unit is equipped with a drive device to activate the switch-over device, said drive device being controlled by means of a control program.
The switch-over device is preferably provided at each spinning station with a control lever for attribution (i.e. application) of the collective drive or of the central auxiliary drive, as desired, to a spinning element, said control lever being pivotable in relation to a hinged cover covering the spinning station. This control lever allows for simple control of the device according to this invention, especially when, in further suitable embodiments according to the object of this invention, the control lever is able to assume three relative positions with respect to the cover, whereby it is flush with the cover in its basic position, pivots away from the cover in its braking position, and is pushed into the cover in its thread joining position.
In order to allow for simple manual control of a device according to this invention, a locking device is suitably provided for the control lever. The operator needs both hands to lift off the bobbin, during the thread joining process, for the search and back-feeding of the thread, for the lowering of the bobbin and to enable (or release) fiber feeding. The locking device ensures that the operator does not also have to hold the control lever in its thread joining position during the thread joining process.
If, in further embodiments according the object of this invention, the locking device is subjected to elastic pressure in such way as to permit the movement of the control lever into the thread joining position while preventing its return into the production position, and if the locking device is furthermore equipped with a controllable solenoid, it becomes possible to control the enabling (i.e. releasing) of the control lever, so that it can return into the production position in a simple manner by means of an electric switch. In such case, the switch is preferably the switching device controlling fiber feeding, whereby the solenoid is then controllably linked to this switching device controlling fiber feeding.
To prevent untimely wear of the main contact roller and of its bearing because of possible imbalance in the spinning element, it is useful to equip the switch-over lever with a damping device. The latter is suitably made in the form of a frictional damper located preferably in the bearings of the switch-over lever.
The above-described device in the assembly makes it possible to carry out thread joining in the simplest and optimal manner. It is especially important for uniformity of yarn characteristics to maintain essentially constant rotor speed during the spinning process. Yarn production begins as early as during the thread joining process, and for this reason, according to the instant invention, thread joining is carried out preferably at a rotor speed that is close to the rotor speed for production, whereby the rotor speed for thread joining should be selected as high as possible as a function of the type of fiber material to be spun, of the rotor diameter, etc.
It has been shown here, as a rule, that optimal results are obtained when the RPMs of the rotor for thread joining are 5% to 25% below the RPMs of the rotor during production.
Use of a device provided in accordance with this invention makes it possible to impose a defined thread joining speed for a desired period of time and at the desired moment upon each spinning element in a simple and reliable manner, without requiring a separate drive for the spinning element at each spinning station. Thus a predetermined thread joining program can be used and the reliability of thread joining is considerably increased in comparison with the known state of the art, while joints become cleaner and stronger.